The effect of mechanical alloying (MA) and preliminary heat treatment (PHT) on phase transformations in Al–Cu–Fe compacts subjected to microwave annealing (MWA) was studied. The initial powder mixtures were subjected to MA for 20 h, after which some of the samples were subjected to PHT at 400°C for 2 h. Then, the samples were pressed and subjected to MWA at different temperatures.
The results showed that ML leads to grain refinement and an increase in the defectiveness of the crystal structure, which accelerates diffusion processes during subsequent MBT. PHT promotes a partial removal of internal stresses introduced by ML and the formation of metastable phases.
Alloys consisting of aluminum, copper and iron are of considerable interest due to their availability, safety of the constituent elements and the ability to form a quasi-crystalline structure. These materials are widely used due to their unique characteristics, such as a low coefficient of friction, high degree of hardness, thermal expansion comparable to metals, low thermal conductivity and moderate electrical conductivity. These alloys demonstrate the ability to form amorphous, crystalline and quasi-crystalline structures. The quasi-crystalline structure (QC) is most often found in alloys based on Al, Zr, Zn, Mg, Ti, while Al-based alloys occupy a leading position due to the variety of methods for their production. The formation of the quasi-crystalline phase in Al-Cu-Fe alloys has always been a priority area of research, since quasicrystals have physical, mechanical and chemical properties different from crystalline materials. The combined properties of CC make them promising for various applications, such as catalysts for steam reforming of methanol, protective coatings, reinforcing components for composite materials, and others.
Among the various methods of producing these materials, mechanical alloying (MA), as a nonequilibrium method, allows for the creation of structures with a uniform composition at relatively low temperatures. This method is characterized by its relative speed and is excellent for obtaining phases that are stable in a narrow range of component ratios and at low temperatures. In this method, all reactions occur in the solid state, which avoids the difficulties associated with solidification during conventional casting. In addition, during mechanical alloying, the final structure of the system is affected by the initial composition of the elements, the duration of milling, heat treatment, energy parameters of milling and other factors.
MBT has a significant effect on the phase composition of the compacts. In the samples subjected to ML only, the formation of intermetallic compounds such as Al2Cu and FeAl3 was observed during MBT. In the samples subjected to PHT, the formation of these phases occurred at lower MBT temperatures.
Microstructure analysis showed that ML and PTO affect the size and distribution of intermetallic phases. ML promotes a more uniform distribution of phases, and PTO increases their size. The results obtained can be used to optimize the processing modes of Al–Cu–Fe alloys in order to obtain materials with specified properties.
Author: Vahid Aghaali, Touradj Ebadzadeh, Zahra Karimi, Asghar Kazemzadeh, Ehsan Marzbanrad
Institute: School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, 16844, Tehran, Iran, Materials and Energy Research Center, Imam Khomeini Blvd, Meshkindasht, P.O. Box 31787-316, Karaj, Iran, University of Waterloo, 200 University Ave W, Waterloo, Ontario, N2L 3G1, Canada